"I was wrong" ... Kevin Rudd talks about his decision to shelve the emissions trading scheme.

He said that as prime minister at the time he took full responsibility for the decision. ''It was a wrong call for which I was responsible,'' he said.

He said he had tried to find a way through the middle to preserve the unity of the government and ''on balance it was the wrong call''.

''You make mistakes in public life, it was a big one.''

The Opposition is expected to seize on Mr Rudd's admission in attempt to further wound Ms Gillard, who after the election put an emissions trading scheme back on the agenda.

Mr Rudd's comments are also likely to cause unrest inside the Labor Party given the debate it will provoke about Ms Gillard. It will do little to dampen suspicions he still considers himself a chance to become the party's leader again.

He said he should have taken more time to talk about policies and he had learnt that he needed to ''sleep more, rest more, and not make bad policy calls on pretty big decisions''.

''I might have learnt a thing or two for the future,'' he said.

The most recent Herald/Nielsen shows more voters prefer Mr Rudd as prime minister than Ms Gillard. Ms Gillard aims to develop a policy to put a price on carbon and have the Parliament pass the legislation before Christmas